Running can be hard on an athlete’s feet and blisters can happen to novice and experienced runners. Many runners rightfully focus on their footwear and making sure they have the right traction and support. However, it is also important to consider how your feet move in the shoes, the surface you’ll be running on, and the environmental conditions you may encounter. For instance, slogging through snow, running through creeks, and training in the rain eventually leads to wet feet. Wet feet early on in a long workout or race lead to macerations and blisters later, and if they form early enough they can be show stoppers.
I know this well, as my first ultramarathon experience was as a crew member for Dean Karnazes during the Badwater Ultramarathon. During Badwater, runners start dumping water on their heads (which eventually ends up in their shoes) beginning at Mile 1. As I was doing research in preparation for the race, two things stuck out: Death Valley would be hot as Hell (duh), and the runners end up with mangled feet.
I immediately made three purchases: an ice bandana, a blister kit, and the book Fixing Your Feet by John Vonhof. When I opened up the package and started rifling through the contents of the blister kit, I had no clue how all the powders, lubricants, tapes, adhesives, and bandages worked. So, I read and I practiced. I would read through a section of my new book, contort my legs to gain access to my foot, apply some concoction of adhesive and tape, and then go run to test out the technique. Every day, I tried something different. As the race neared, I was obsessed. To put some of these newfound techniques to the ultimate test, and to mirror the conditions of the race, I routinely soaked my laced-up feet with the garden hose before setting out on a run and splashed through every puddle and stream I could find.
Since then, I have reinforced my blister prevention and treatment arsenal with a simple red plastic toolbox from the Home Depot. The box is filled with an array of products to help repair feet when they become battered, bruised, bloodied, and blistered. Admittedly, the toolbox is a bit rickshaw, somewhere between the basic necessities and a full-blown medical kit, but it is mine, and I know how to use every product in it. I bring it with me whenever I attend an ultramarathon as a coach or as an athlete. Often it remains idle. At other races it is a lifeline for athletes. I take comfort in knowing that if athletes do run into trouble with their feet, I have some level of skill to patch them up and get them on their way.
How Blisters Stop Runners in Their Tracks
Your feet propel you forward. When your foot is damaged, it affects the entire kinetic chain from the ankle, to the knee, and through the hip. You might be able to limp through for a while on a blistered foot, but chances are that the change in biomechanics will eventually catch up with you and compound the issues you face.
In many cases, it’s not the blister that leads to the DNF. The blister just starts the process by changing the way you run, and over time those changes lead to other biomechanical problems, slowing you down, knocking you off your nutritional strategy, exposing you to the elements longer, and so forth. This does not have to be the case. Blisters can be largely prevented through training, prevention, a little treatment know-how, and better race day management. Treatment is relatively easy, requiring a few basic products and skills to fix the majority of issues. It takes practice, but it’s worth it.
Preventing and Treating Blisters
Whenever you stress an organ or a structure in your body beyond its capabilities, you cause damage. Ultramarathons normally represent a longer, more difficult run than your day-to-day training, complicated by the fact most ultramarathon events occur in areas away from your home training grounds. The trail surface, camber, dirt, dust, and debris your feet encounter are undoubtedly different during the race than at home. Furthermore, your biomechanics are different, depending on the properties of the trails, placing stresses on different areas of the skin of the foot. Therefore, the shoe/sock/powder/tape/lubricant/insole combination that worked in training may not always work during the race.
Just as training on flat ground will not completely prepare you for a mountainous ultra, training on your home trails might not fully prepare your feet for the rigors of race day. Therefore, a combination of education, preventive measures, and wound care skills offers the most comprehensive way to ensure that your hard-earned training does not come undone by the unraveling of your feet on race day.
Science of Blister Formation
Start with friction
What runners commonly refer to as a blister is clinically termed a friction blister because friction is the primary culprit. Although heat and moisture are contributing factors, friction and the underlying shear forces are what ultimately cause the dreaded blister. At foot strike, the ground pushes backward on your shoe, your insole pushes backward on your sock, and your sock pushes backward on your skin. As you push off the ground, these forces between your skin and sock, sock and insole, and shoe and ground all reverse direction.
The problem is that the surface of your skin is pliable (after all, it is called soft tissue). As your body applies these shear forces, your soft tissue (skin on the feet) moves more than your skeletal system (rigid bone). This out-of-sync movement between your skeleton, soft tissue, sock/shoe, and shoe/ground is what ultimately causes the frictional force that leads to a blister. Your shoe and sock move against your outer layer of skin (epidermis) more than your outer layer of skin moves against your inner layer of skin (dermis).
As the bump and grind between these two skin layers continues, the layers eventually separate. Once this separation occurs, fluid fills the void due to hydrostatic pressure. The result is a fluid sac between the newly separated layers of skin bordered by yet-to-be separated layers along the edges.
Add Heat and Moisture
The addition of heat and moisture exacerbates blister formation. Heat accelerates the blistering process primarily by loosening the bond between the dermis and epidermis. Research has demonstrated that an increase in skin temperature of 4°C will accelerate blister formation by 50 percent (Kiistala 1972). Increases in foot skin temperature, heat from the environment, increases in metabolic response, and heat from frictional forces all add to the heat within your shoes. Furthermore, the warmer your feet are, the more they sweat. The more your feet sweat, the more saturated your socks, shoes, and skin become.
Dumping water on your head, running through a river crossing, and running in the rain all accomplish the same feat (excuse the pun). They increase the moisture in your shoe, in your sock, and on the skin of your foot. This moisture further increases the frictional forces between your foot and sock with every foot strike, adding to blister susceptibility (Naylor 1955). Furthermore, the moisture weakens the outer layer of skin, making it more prone to injury.
And complicate with hydration status
While heat, trauma, and moisture are attacking your skin from the outside, on the inside your hydration status can also make you more susceptible to blisters. If a runner becomes even slightly hyponatremic (having low blood sodium), one of the body’s protective mechanisms – long before blood sodium levels are dangerously low – is to pull water out of the plasma into the extracellular space, thus increasing the concentration of sodium in the blood. As a simple by-product of gravity, this fluid in the extracellular space pools in the extremities, commonly resulting in puffy hands or feet.
Unlike your hands, your feet are subject to the rigors of propelling you forward. The increased fluid in the extracellular space in the skin of your feet accelerates the blistering process. It causes your feet to get bigger, turning your once perfectly broken-in shoes into a friction-laden trap. It also loosens the skin layers, as fluid is more easily pushed between the dermis and epidermis.
Preventing Running Blisters: Training, Gear, and Protection
Each of the three aforementioned blister factors of friction, heat, and moisture can be alleviated with the right combination (in order of priority) of training, gear (shoes and socks), race day preventive measures, and finally, treatment.
How Training Influences Blister Formation
Training is the first level of prevention in blister formation. Your skin adapts to stress just like any other organ in your body. Many studies, primarily involving the military, have demonstrated that gradual exposure to frictional forces on the foot (through hikes and marches) decreases the skin’s susceptibility to blisters (Allan 1964; Hodges, DuClos, and Schnitzer 1975; Knapik et al. 1995).
As you train, your epidermal skin cells become thicker and in theory more cohesive, making them more resistant to blistering. How does this happen? As you run, you slough off skin cells faster than normal. These are rapidly replaced by new skin cells, but these young cells don’t get the chance to differentiate into layer-specific cells (epidermis, dermis) before they are stressed by another run (S. H. Kim et al. 2010). When this happens frequently over a relatively short time, it results in a thickening of the skin and eventually a callus (which you should keep shaved down).
How Shoe and Sock Choice Influences Blister Formation
Your shoe and sock combination is the next level of blister prevention. With respect to blister prevention, your shoe/sock combination should serve the dual purposes of reducing frictional forces between your skin/sock and sock/shoe and managing moisture transfer from your foot into the air. Some socks that segregate the toes (toe socks) also aim to reduce the skin-to-skin friction between the toes.
Overwhelming research has shown that a well-fitting wicking sock offers the best blister prevention strategy (Herring and Richie 1990; Knapik et al. 1995, 1996). Fortunately, most sock companies are now wise to this idea and are moving away from thicker, bulkier, and less wicking socks for runners and ultrarunners. Shoe companies are following suit. Materials for shoes are constantly becoming more pliant and breathable, and shoes are available in a wider variety of shapes and sizes. Perhaps blister prevention is not the shoe manufacturers’ end goal, but the improvements in materials and fit do help.
Your shoe/sock combination should be tested in training, and shoe trials should be completed early in the season. It is important to figure out what works and what doesn’t far out from your event so you can ramp up your training without fear of damaging your feet. Along these lines, once you find the combination that works for you, I recommend investing in enough shoes and socks to get you through the entire season. Ultrarunners burn through shoes and socks, and designs or availability can change unexpectedly. You don’t want to be searching for new shoes or having to switch to a new model or design in the middle of the season when your training workload is very high.
Treating Running Blisters
One lesson I’ve learned from racing and crewing ultramarathons, and from watching the parade of mangled feet at Badwater, is that athletes use an incredibly wide range of techniques to prevent blisters on race day. Some use tape, some use lubricants, other use powders. The more creative (or desperate?) ultrarunners will use elaborate combinations and concoctions, sometimes taking hours to apply.
In many cases, two runners will use techniques with opposing goals (keep the skin from moving versus encourage the skin to move with less friction), and both techniques may (or may not) work. This reinforces the ‘find what works for you’ advice from Fixing Your Feet, Jon Vonhof’s bible of blister prevention and treatment, which makes the point by providing numerous personal N of 1 anecdotes from athletes. From a scientific standpoint, this advice rings true. In fact, there is little scientific evidence that any of the aforementioned strategies work.
Furthermore, there is conflicting research that indicates some preventive measures actually exacerbate the problem by adding moisture and increasing the skin’s coefficient of friction (Allan and Macmillan 1963; Allan 1964; Quinn 1967; Nacht et al. 1981; Knapik et al. 1995; Reynolds et al. 1995; Knapik, Reynolds, and Barson 1998).
This is an area where less is more. The prevention strategies we know work are training (conditioning the feet to handle the stresses of long miles) and an effective shoe/sock combination. These should always be your starting points. Adding other techniques like tape, lubricant, powder, or antiperspirant increases complexity, adds more variables to any training or race day situation, and might exacerbate the problem. Nonetheless, many athletes continue to go far beyond training and shoe/sock choices to solve recurrent skin issues with their feet; for them, it is worth the effort to find a minimal solution.
It is also important to realize there is no combination of equipment or amount of training that will entirely eliminate the risk of developing blisters during training or on race day. You can minimize these risks as much as possible, but you also have to learn to patch and repair a blister in the field when things go wrong.
Fix a Running Blister or Forget It?
If you do get a blister (or the precursor, which is referred to as a “hot spot”), you have a decision to make: You can save some time and continue running, or stop and lose some time treating your feet. In making this decision, you need to balance your race-day goals, performance expectations, safety, and race situation. Generally speaking, the more time you have left to run and the bigger the problem could become, the more it is worth your while to take a few minutes and fix what is wrong. Don’t let little problems become big problems. My advice is to always err on the side of caution and fix problems early, particularly at the 100K and 100-mile distances, where there is a lot of ground to cover.
If you are in a situation where you choose not to stop and fix a blister, or you are many miles from the next aid station and you have no products to treat the blister, it is time to suck it up. Blisters hurt because the foot is highly innervated, and runners tend to find relief by changing their gait or foot-strike pattern. While this is a logical strategy (“I have pain there, I am going to try to avoid it”), the ramifications of changing your gait too much can have consequences up the kinetic chain.
Your foot, ankle, knee, and hip are all connected and constantly affect one another. Although I am an advocate for manipulating gait and biomechanics in an effort to combat muscular fatigue, I do not advocate doing so in the context of a blister. In this case it’s time to be tough and keep your gait as normal as possible. Running with your normal gait may make the blister worse, but that’s still only one problem, and one you can treat and get under control. Changing your gait to “run around a blister” can lead to pain or injuries you can’t effectively treat and control while continuing to race. That said, you might have to tough it out and run on a blister on race day, but it’s not a strategy to rely on. Blisters can and should be prevented and treated.
Fixing Blisters on the Run
Blisters come in a variety of shapes, sizes, and levels of discomfort. Treatments also come in many shapes and forms. Unless you are a medical professional with many years of blister management experience, a simple solution is always best. I have found success with the following nine-step plan:
- Clean the surface of the blister and the surrounding skin. If an alcohol pad or disinfectant is available, use it. If not, it is still usually best to proceed to step 2. You are less prone to infection if you can properly manage the blister while it is small and treatable. Large broken blisters will become more prone to infection more readily than small broken blisters. There is more opportunity to become infected through the larger area of damaged and exposed skin.
- Puncture the blister with a needle, sharp scissors, or scalpel. Take care to puncture the blister enough to allow fluid to drain. However, don’t open it so much that the blister roof becomes detached. If you are using a needle (safety pins from a race number also work well), put three to four holes in the blister so that it will drain. Ideally, place the punctures such that fluid can continue to drain while you keep on running.
- Squeeze the fluid out of the blister.
- Clean and dry the surface of the blister and the surrounding skin. You are now prepping the skin to apply a patch, so ensure that it is dry and free of debris. You can choose to add a very small dab of lubricant to the blister roof. This is to prevent the patch from sticking to the blister roof when you eventually peel the tape off.
- Size up the area you are going to patch. Then cut a piece of tape or bandage to cover the blister. The patch should be large enough so that it can stick to the surrounding skin. If the blister is on a toe, this might mean wrapping the entire toe. If you do have to wrap a toe, it’s usually best to wrap the adjacent toes also. This way, the tape does not rub directly on adjacent skin.
- Apply a tape adhesive such as tincture of benzoin to the area surrounding the blister. Although the tape has its own adhesive backing, using an additional tape adhesive will ensure a better stick.
- Place the tape down on the skin from one edge of the tape to the other. Be careful to avoid folds and creases. If you do get a fold or a crease, start over.
- Lightly press down on the patch to ensure the adhesive completely sticks to the skin.
- Put your socks on, lace up your shoes, and run!
If you are particularly blister prone, practice various techniques at home. Cutting and placing the patch on the surface of the skin can be the most frustrating part of the process during a race. The tape is sticky and adheres to itself and to your fingers. You’re in a hurry. You’re sweaty and dirty. And you’re working in a dirty, dusty environment. Finding a routine and learning simple skills makes the process smoother and faster in race conditions. As with any other skill, practice makes perfect!
What a Running Blister Kit Should Contain
This assortment will be enough to fix minor and moderate blisters in the field and keep you moving. It is neither a substitute for a full medical kit nor what you would use to treat skin injuries after a race.
- Adhesive felt sheet or moleskin
- Needles or small scalpel (size 11)
- Alcohol pads or Betadine swabs
- Kinesio tape, Elastikon tape, or Leukotape (to patch or prevent). I highly prefer Kineso Tape
- Adhesive such as tincture of benzoin
- Lubricant such as Bodyglide or BlisterShield or Squirrel’s Nut Butter
- Gauze pads
Adapted from “Training Essentials for Ultrarunning”, by Jason Koop and Jim Rutberg.
- Allan, J. R., 1964. A Study of Foot Blisters. United Kingdom: Army Operational Research Establishment.
- Allan, J. R., and A. L. Macmillan. 1963. “The Immediate Effects of Heat on Unacclimatized Paratroops: Exercise ‘Tiger Brew II.’” Research memorandum. United Kingdom: Army Operational Research Establishment. Report No. 16/62.
- Hodges, G. R., T. W. DuClos, and J. S. Schnitzer. 1975. “Inflammatory Foot Lesions in Naval Recruits: Significance and Lack of Response to Antibiotic Therapy.” Military Medicine 140 (2): 94.
- Kiistala, U. 1972b. “Dermal-Epidermal Separation. II. External Factors in Suction Blister Formation with Special Reference to the Effect of Temperature.” Annals of Clinical Research 4 (4): 236–246.
- Knapik, Joseph J., Katy L. Reynolds, Kathryn L. Duplantis, and Bruce H. Jones. 1995. “Friction Blisters.” Sports Medicine 20 (3): 136–147.
- Knapik, Joseph J., Murray P. Hamlet, Kenneth J. Thompson, and Bruce H. Jones. 1996. “Influence of Boot-Sock Systems on Frequency and Severity of Foot Blisters.” Military Medicine 161 (10): 594–598.
- Knapik, Joseph J., Katy Reynolds, and John Barson. 1998. “Influence of an Antiperspirant on Foot Blister Incidence During Cross-Country Hiking.” Journal of the American Academy of Dermatology 39 (2): 202–206.
- Nacht, Sergio, Jo-Ann Close, David Yeung, and Eugene H. Gans. 1981. “Skin Friction Coefficient: Changes Induced by Skin Hydration and Emollient Application and Correlation with Perceived Skin Feel.” Journal of the Society of Cosmetic Chemists 32 (2): 55–65.
- Naylor, P. F. D. 1955. “The Skin Surface and Friction.” British Journal of Dermatology 67 (7): 239–248.
- Quinn, J. 1967. “The Effects of Two New Foot Powders on the Incidence of Foot Infection and Blisters in Recruits During Basic Training.” Research Memorandum. Farnborurogh, United Kingdom: Army Personnel Research Establishment. Report No. P/6.
- Reynolds, Katy, Andre Darrigrand, Donald Roberts, Joseph Knapik, Jon Pollard, Kathryn Duplantis, and Bruce Jones. 1995. “Effects of an Antiperspirant with Emollients on Foot-Sweat Accumulation and Blister Formation While Walking in the Heat.” Journal of the American Academy of Dermatology 33 (4): 626–630.
- Vonhof, John. 2011. Fixing Your Feet: Prevention and Treatments for Athletes. Birmingham, AL: Wilderness Press.